Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$212.53	3.315%	$219.5754	$219.58	$219.60	$219.60
Purchase #2	$36.26	10.784%	$40.1703	$40.17	$40.15	$40.20
Purchase #3	$54.53	12.492%	$61.3419	$61.34	$61.35	$61.30
Purchase #4	$144.89	12.350%	$162.7839	$162.78	$162.80	$162.80
Purchase #5	$67.34	5.196%	$70.839	$70.84	$70.85	$70.80
Purchase #6	$14.26	4.481%	$14.899	$14.90	$14.90	$14.90
Purchase #7	$123.61	13.458%	$140.2454	$140.25	$140.25	$140.20
7 purchase totals =	$653.42		$709.8549	$709.86	$709.90	$709.80